The present invention relates to a scroll type compressor applied to a coolant compressor of a freezer, an air conditioner or the like and, more particularly, to weight reduction of an Oldham ring and improvement of wear resistance of its sliding surface.
A swivel scroll which is a movable member in a scroll type compressor, and an Oldham ring serving to prevent the swivel scroll from revolving on its own axis, are generally made of cast iron or steel.
However, the operation at a higher speed has been achieved in accordance with a recent progress in the inverter driving technique, and it has been hoped eagerly to reduce the weights of the swivel scroll and the Oldham ring which are movable members, in order to decrease the centrifugal stress and the acceleration stress. Weight reduction of such members has been realized by making a swivel scroll and an Oldham ring of an aluminum alloy and subjecting the sliding surfaces of these two members to electroless Ni plating, as disclosed in JP-A-1-237376, or by adopting a dipping method so that the sliding surface of an Oldham ring made of an aluminum alloy is formed of a different metal plate, as disclosed in Japanese Patent Application No. 03-236268. Moreover, there have been proposed an Oldham ring whose sliding surface is coated with iron or an iron base alloy by thermal spray and an Oldham ring whose sliding surface is coated by electroless Ni--P plating.
In the example of the conventional technique in which both a swivel scroll and an Oldham ring are formed of an aluminum alloy, abnormal wear caused by seizure, scuffing or the like owing to the sliding contact between aluminum members which is a contact between members of the same kind of metal, and corrosion resistance are matters to be considered. The example in which the sliding surface of an Oldham ring is coated with iron or an iron base alloy by thermal spray encounters problems such as deterioration of the precision of parts caused as a result of the thermal-spray coating treatment, and additional cost resulting from the surface treatment. Further, in the example in which the sliding surface of an Oldham ring is subjected to electroless Ni--P plating in accordance with the conventional method, bonding strength between the Oldham ring and the Ni--P plating is not satisfactorily high, which results in a problem of local separation of the plating. Also, since the micro-Vickers hardness of the Ni--P plating formed by the conventional method is 500 or less, the thickness of the plating must be increased to some extent in consideration of wear resistance at the time of sliding movement. Therefore, when the plating thickness is increased, uniformity in the plating thickness is deteriorated to cause partial contact between the Oldham ring and the associated member, which results in abnormal wear and abnormal seizure.
The present invention has been achieved in such a technical background, and it is an object of the invention to solve the above-described problems and to provide an Oldham ring of a scroll type compressor which is excellent in wear resistance, seizure resistance and durability which particularly matter at the time of high-speed operation.